Process of purifying alkaline chlorids.



UNITED STATES PATENT OFFICE.

CHARLES H. DASI-IER, OF OA'KLAND C'ALIFOR NIA.

'PROCESS OF PURIFYING ALKALINE CHLOBIDS.

956,303. No Drawing.

To all whom it may concern:

Be it known that I, CHARLES H. DAsHER, a citizen of the United States,residing at Oakland, in the county of Alameda and State of California,have'invented new and useful Improvements in Processes of PurifyingAlkaline Chlorids, of which the following :is a specification. Theobject of this invention is the separation of the. alkaline earths andearth metals such as calcium, magnesium and aluminum from chlorids ofsodium and potassium, whereby a salt of high purity either for householdpurposes or ortelectrolyzing either fused or 1n water solution isproduced. As this process has particular application to purifying sodiumchlorid, this salt will be considered specifically, it being understoodthat the process is equally applicable to potassium chlorid or a mixtureof the salts.

The sodium chlorid produced by evaporation from sea-water and salt lakesand by mining from deposits of crystallized salt generally contains asimpurities the chlorids and sulfates of calcium and magnesium withtraces of iron and aluminum salts. There is often considerable or 'anicmatter. This impure sodium chlorid ses at about 780 centigrade to a veryfluid mass, and if the temperature is not allowed-to rise much above 800centigrade little volatilization takes place. The organic matter mayentirely burn out during fusion or finely divided carbon from itsreduction may remain in suspension. The impurities are all in solutionor suspension in the liquid sodium chlorid. If silica (SiO and eithersodium carbonate (Na CO or sodium bicarbonate (NaHCO be added to thefused chlorid, the carbonate rapidly dissolves and a violent reactionensues with the evolution of gas. The silica changes to a pasty massthat gradually settles through the fused chlorid as the evolution of gasdiminishes. This reaction, for instance in the case of salt containingmagnesium chlorid and magnesium sulfate, is probably of the followingtype:

the final result being the reduction of all the alkaline earths andearth metals to silicates and the production of sodium chlorid andsulfate in their place.

The amount of carbonate used is deter- Speciflcation of Letters Patent.Patented Apr. 26, 1910- Application filed September 20, 1909. Serial No.518,791.

mined according to the above reaction for the complete conversion of theimpurities present into silicates; but I use a relatively greater massof silica than shown b the above reaction and treat the fused sat for asufficient length of time to form silicates more highly siliceous thanthe metasilicate 'shown by the above reaction. This is probably. of thefollowing type:

in the mass is removed by the CO gas ac-' cording to the reaction CO+C=2CO or is mechanically infolded by the pasty silicates. I

A convenient way of providing sufficient mass of silica is to have thefurnace wherein fusion takes place lined with it; though any lining onwhich the fused salt has no action, as fire clay, may be used and thenecessary silica added to the charge at any convenienttime.

When the treatment is finished the liquid salt is drawn from the furnaceand the precipitated silicates may be separately removed. If completesubsidence of the silicates has not occurred and particles are insuspension, the liquid salt may be filtered through sand of silica orany neutral substance contained in a proper receptacle and helated tothe temperature of fusion of the sa t.

Having described my process, what I claim and desire to secure byLetters-Patent, is:

1. The method of purifying sodium chlorid which consists in fusing it sothat all the impurities are in solution or suspension, and adding silicaand a sodium salt to the fused mass, the amount of silica used beingsufficient to produce silicates that are insoluble in the fused sodiumchlorid.

2. The method of purifying sodium chlorid which consists in fusin thesalt at approximately 780 centigra e, adding silica and a suitablealkaline carbonate to decompose and precipitate the impurities assilicates, and then separating the purified salt from the precipitatedimpurities.

3. The method of purifying sodium chlorid which consists in fusing thesalt at approximately 780 centigrate, adding silica and a suitablealkaline carbonate to decompose and precipitate the impurities assilicates, and then separating the purified salt from the precipitatedimpurities, the amount of silica above added being sufiicient to producesilicates that are insoluble in the fused mass, and infusible at saidtemperature.

4. The method of purifying sodium chlorid which consists in fusing it,adding silica and sodium carbonate and continuing the fusion until thesilica changes to a pasty mass that gradually settles through the fusedchlorid as the evolution of gas diminishes, the amount of the carbonateand silica used being suflicient for the complete conversion of theimpurities present intoinsoluble and infusible silicates.

5. The method of purifying sodium chlorid Which consists in fusing thesalt at approximately 7 80 centigrade so that all the impurities are insolution or suspension, adding thereto silica and sodium carbonate todecompose and precipitate the impurities as silicates, the amount ofsilica added being sufiicient to produce silicates that are insoluble inthe fused salt and infusible at said temperature, and then separatingthe purified salt from the precipitated impurities by either decantationor filtration.

In testimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

CHARLES H. DASHER.

